Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylic acid is a stronger acid than phenol. Why?
Answers
When we react a compound with HCN then will see that the nucleophile will show the attacking species reaction CN-.
Hence the negativity of the compound will go up which will result in the decrement of HCN. The compound will show the +I effect that will increase.
Hence you can arrange the compound in terms of its reactivity with HCN:
Di-tert-butyl ketone < Methyl tert-butyl ketone < Acetone < Acetaldehyde
Answer
Although phenoxide ion has five resonating structures than carboxylate ion has only two resonating structures but still carboxylic acids are stronger acids than the phenol because in carboxylate ion (conjugate base), negative charge dispersed between two electro negative oxygen atoms.
Whereas in phenoxide ion (conjugate base of phenol), negative charge is dispersed or delocalised less effectively over one oxygen atom and less electro-negative carbon atom.
[ Refer the attachment for resonating structures of Phenoxide ion and Carboxylate ion ]
